1. Field of the Invention
The present invention relates to lane tracking systems for vehicle positioning and safety applications and more generally relates to imaging systems and methods for vehicle positioning and safety applications.
2. Description of the Prior Art and Related Information
The capabilities of modern image processing systems have provided an opportunity for improving vehicle occupant safety and vehicle guidance. In particular, lane tracking systems have been proposed which can monitor the vehicle position by imaging a roadway and detecting lane markers. Such lane tracking systems can be used to warn the driver when the vehicle is about to leave a lane, or in more advanced systems may even be used for automated vehicle guidance systems. In such lane tracking systems, the camera records images of the roadway in front of the vehicle and imaging processing software isolates the lane markers from the roadway. The vehicle position is then determined relative to the lane markers by additional processing software.
For such lane tracking systems to be effective for vehicle occupant safety, vehicle guidance or other applications it is important that the lane tracking be effective under most if not all conditions which will be encountered in real world applications. However, this is very difficult in practice. For example, a variety of difficult lighting conditions may commonly occur which make it much more difficult for the imaging system to accurately determine lane markers and vehicle position. One such example of a common difficult imaging condition is bright sunlight where glare off the roadway can saturate the image so the roadway lane markers cannot be accurately detected. Another example is nighttime driving where oncoming headlights can saturate the imaging system making it impossible to detect lane markers illuminated by the vehicle headlights. Since these are very common situations which can continue for hours at a time, if these situations cannot be adequately dealt with the usefulness of a lane tracking system in a vehicle is substantially diminished.
Prior approaches to this problem of poor lane imaging under harsh lighting conditions have tried to increase the sophistication of the imaging devices, i.e., use more sophisticated cameras, or use more sophisticated image processing algorithms to increase the ability of the imaging system to detect the lane markers despite the poor image quality. Such approaches to solving the problem may become extremely complex and costly, both to design and to implement due to the cost of the imaging hardware and the more powerful image processors required. Also, despite such added cost and complexity the image itself cannot be controlled and such a brute force approach may not be successful in all of the lighting conditions which will be experienced in real world applications. Also, the cost constraints of the particular application may make very complex and costly solutions impractical whereas lower cost hardware and software systems cannot adequately deal with the problem.
Accordingly, a need presently exists for a system and method for detecting lane markers in a roadway for vehicle occupant safety and other applications which can provide accurate lane marker detection under a variety of difficult lighting conditions.